J.Jpn. Surg. Soc.. 127(3): 295-304, 2026

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Feature topic

EVOLUTION OF MEDICAL TREATMENT FOR BREAST CANCER BASED ON GENOMIC INFORMATION AND THE DEVELOPMENT OF PRECISION MEDICINE

Breast cancer therapy has transitioned from uniform, morphology-based approaches to an era of precision medicine guided by multiomic biomarkers. Historically, the identification of hormone receptors (estrogen and progesterone) and HER2 overexpression established early paradigms for individualized therapy. In the modern era, high-throughput techniques enable comprehensive tumor profiling beyond the classical subtypes, revealing intrinsic molecular subgroups and actionable mutations. In early-stage breast cancer, multigene assays (e.g., Oncotype DX) refine adjuvant chemotherapy decisions, while emerging strategies like circulating tumor DNA (ctDNA) monitoring promise to detect minimal/molecular residual disease (MRD) and guide postoperative therapy intensification or deescalation. In metastatic disease, genomic alterations such as BRCA1/2, PIK3CA, AKT1, PTEN, and ESR1 mutations inform the use of PARP inhibitors, PI3K/AKT/mTOR pathway inhibitors, and next-generation endocrine therapies, respectively. Comprehensive genomic profiling (CGP) is now integrated into practice to identify uncommon biomarkers (TMB-H, MSI-H, NTRK fusions, etc.), although challenges remain in timing and utility and currently only a minority of patients receive matched therapies. This article reviews the historical progression of breast cancer systemic therapy from histopathologic classification to today’s multiomic precision medicine approach and discusses current advances and future perspectives in individualized treatment strategies across early and advanced breast cancer.

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